The present invention concerns an acrylourethane polymer useful in high solids coating compositions.
Environmental and economic concerns often make it desirable to minimize the quantity of organic solvent released to the atmosphere in the application of paints, such as to automobiles, either in single color coats or in color coat/clear coat or other applications. One way to do this is to make a paint with higher solids content which contains less solvent to evaporate. Several properties must be balanced and reconciled in developing such a paint.
It would be desirable to have polymers which can be used to make paints with relatively high solids content and low viscosity.
While acrylourethane coating compositions are known including U.S. Pat. Nos. 4,304,706 (1981); 4,208,494 (1980); 4,208,495 (1980); 3,975,457 (1976); and 3,919,351 (1975) all to Chang et al, it is difficult to find combinations and proportions of acrylic, diol and diisocyanate that will not gel on reaction. In U.S. Pat. No. 4,208,495, Example 1 uses certain monoalcohols during the reaction to avoid gelling, however, the low level of hydroxyl ethyl acrylate such as 9% or less does not permit suitable curing at bake temperatures as low as might be desired.